2,3-Dichloro-5,6-dicyanopyrazine and derivatives

ABSTRACT

Certain amino derivatives of 2,3-dichloro-5,6-dicyanopyrazine are useful fluorescing agents.

United States Patent 1 Donald 1 Apr. 22, 1975 1 1 2.3-DICIILORO-5.6-DICYANOPYRAZINE AND DERIVATIVES [75] Inventor: Dennis Scott Donald, Mendenhall.

[73] Assignee: E. I. du Pont de Nemours and Company, Wilmington, Del.

['22] Filed: Sept. 25, 1973 [21] Appl. No.: 400,505

[52] U.S. Cl. 260/250 BN; 8/1 D; 8/1 W;

8/77; 117/335 T. 252/3012 W [51] Int. Cl C07d 51/76 [58] Field of Search 260/250 RB. 250 EN [56] References Cited UNITED STATES PATENTS 1/1962 Daglish ct a1. 260/250 RBN 12/1971 Grahowski et ul 260/250 RBN OTHER PUBLICATIONS Theilheimer. Synthetic Methods of Organic Chemistry. pp. 264-265, (1964). Klaus et 21]., Chemical Abstracts. 78:7l364t, (1973),

of Tetrahedron Letters. No. 47. pp. 4771-4774. (1972).

Primary Examiner-Alton D. Rollins Assistant E.\'aminer-Ralph D. McCloud [57] ABSTRACT Certain amino derivatives of 2,3-dichloro-5.6- dicyan'opyrazine are useful fluorescing agents.

3 Claims, No Drawings 2,3-DICHLORO-5,6-DICYANOPYRAZINE AND DERIVATIVES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to novel pyrazine derivatives and to methods of making the same.

2. Description of the Prior Art Percompounds have been known for a number of years. For example, tetrafluoroethylene and other perhalogenated compounds are widely known and used in polymers, stable fluids and numerous other applications. Percyano and polycyano compounds. e.g., tetracyanoethylene, are also known and their chemistry reviewed in Chapter 9 in Z. Rappaport. The Chemistry of the Cyano Group", John Wiley and Sons. Interscience Publishers, 1970. These polycyano compounds frequently undergo nucleophilic displacement reactions unique to compounds highly substituted by cyano groups. No art appears to exist, however. disclosing the compounds of the present invention.

DESCRIPTION OF THE INVENTION The invention comprises a compound of the general formula:

NC x no t at (I) wherein X is NI-I NHR and NRR', in which R and R, alike or different, are alkyl of l to 6 carbon atoms or alkenyl of 3 to 6 carbon atoms with the proviso that an unsaturated carbon of the alkenyl group is not directly attached to nitrogen.

The invention also comprises an improved process for the preparation of the 2,3-dichloro-5,6- dicyanopyrazine which is used as the starting material for making the aforesaid compounds. It is prepared by reaction of the known compound, l,4,5,6-tetrahydro- 5,6-dioxo-2,3-pyrazinedicarbonitrile, with thionyl chloride as shown:

H NC N o N N 01 I I +soc1 ()1 NC N -o N N 01 The reaction is ordinarily carried out using excess thionyl chloride as reaction medium. Other chlorinating agents, e.g., phosphorus oxychloride, phosphorus pentachloride, and mixtures of these may be used, but thionyl chloride is preferred. The use of a tertiary amine as a base to remove the by-product hydrogen chloride from the reaction mixture can be employed. Suitable such bases include pyridine, collidine, N,N- dimethylaniline, and other tertiary aromatic amines.

It is preferred to carry out the reaction in the pres enee of a catalytic amount of dimethylformamide or dimethylacetamide to give an improved yield of product. The quantity of the catalytic amide should be at least 0.02 mole per mole of l,4,5,6-tetrahydro-5,6 dioxo-Z,3-pyrazinedicarbonitrile, preferably 0.1 to 0.5 mole per mole. Larger amounts can be used if desired.

NC 1}! c1 10] +2X-H ----9 NC -c1 N NCL N x 01 m 01 NC N 01 wherein X has the values set out above.

Amines react readily with the dichloro-substituted pyrazine at about room temperature or below. and it is preferred to employ temperatures of to 30C at atmospheric pressure. Reaction times for complete reaction range from a few minutes to several hours depending upon the reaction temperature and the particular amine employed.

The reaction is normally carried out in a nonprotic polar solvent. Examples of suitable solvents include tetrahydrofuran, acetone, acetonitrile, dimethylsulfoxide.

Z-methoxyethyl ether (diglyme), 1,2-dimethoxyethane (glyme), and ethyl acetate. It is preferred to employ tetrahydrofuran as solvent.

Two moles of amine reactant are required for each mole of 2,3-dichloro-5,6dicyanopyrazine to effect replacement of one of the chlorine atoms since the second mole reacts with the liberated HCI as shown in the equation above. A slight excess of amine over that required may be employed, i.e., about 2.1 moles of amine per mole of starting pyrazine.

SPECIFIC EMBODIMENTS OF THE INVENTION The following examples illustrate the invention and all parts are by weight and all temperatures are in degrees Centigrade unless stated otherwise.

EXAMPLE 1 2,3-Dichloro-5,o-dicyanopyrazine (l a N NC N o N (:1 I I $001 ()1 NC- N 0 NC N at To a mixture of 4.80 g. (30 mmoles) of l,4,5,6- tetrahydro-S,6-dioxo-2,3-pyrazinedicarbonitrile, prepared by the method of Bredereck and Schmdtzer, Ann., 600. (1956), in ml ofthionyl chloride was added slowly at 25 4.74 g (60 mmoles) of pyridine.

The mixture was heated under reflux for 18 hours. and the starting material was completely dissolved after this time. Excess thionyl chloride was distilled at reduced pressure. and the residual dark, viscous oil was dissolved in methylene chloride. This solution was successively extracted with water, aqueous sodium bicarbonate solution and finally with water. The organic layer was dried and the solvent removed to leave 2,3- dichloro-S,6-dicyanopyrazine as a yellow solid. The product was purified by recrystallization from chloroform to give 1.37 g (23.4%) of purified product as white prisms, mp 179-l80. Alternatively, 2,3- dichloro-S,6-dicyanopyrazine may be purified by sublimation.

Additional analytical data were obtained on another sample of the product, prepared as described in Example 4, mp 206.0208.0.

2-Amino-3-chloro-5,6-dicyanopyrazine (2) UV: A ,"I"" 304 mp. (e 8300); 253 my. (e 11.700);

211 my. (e 26,900). Anal. Calcd for C N CI C, 36.20; N, 28.19; Cl, 35.61 Found: C, 35.88; N, 28.06; Cl, 35.04

EXAMPLE 2 A solution of 5.00 g (25.1 mmoles) of 2,3-drchloro- 2.3-Dichloro-5,6-dicyanopyrazine (l) A mechanically stirred slurry consisting of 81.0 g (0.50 mol) of 1,4,5,6-tetrahydro-5,6-dioxo-2,3- pyrazinedicarbonitrile, 8.0 ml of dimethylformamide and 1600 ml of thionyl chloride was heated under a nitrogen atmosphere and gas evolution began at ca. 62. After 3.5 hours the solid had dissolved and the temperature had risen to 70. After cooling to room temperature a Dry Ice/acetone bath was applied until the temperature of the reaction medium was 65. The crystals which formed were collected by rapid filtration of the cold slurry under nitrogen. The solid was washed twice with l50-ml portions of cold diethyl ether and air-dried to give 69.9 g (70%) of 2,3-dichloro-5,6- dicyanopyrazine. Recrystallization of the product from 600 ml of chloroform with carbon treatment gave 51.4

g of purified product.

EXAMPLE 3 Z-Amino-3-chlor0-5,6-dicyanopyrazine 2 NC N 01 21m NC c1 3 NC N 21m mr cl NC N 01 A total of 55 mg of 2,3-dichloro-5,o-dicyanopyrazine 5,6-dicyanopyrazine 1 in 50 ml of anhydrous tetrahydrofuran was cooled to 70 in a Dry Ice-acetone bath. Anhydrous ammonia was passed slowly over the rapidly stirred solution for 5 minutes during which time the temperature rose to 5 5 and yellow microcrystals formed. The still-cold reaction mixture was poured into 300 ml of water to precipitate, after water wash and airdrying, 3.45 g (81%) of nearly pure 2-amino-3-chloro- 5,6-dicyanopyrazine (2) as a yellow powder. Careful acidification of the cold mother liquor to pH 2 and evaporation to dryness on a rotary evaporator gave 0.60 g of slightly less pure product. Two recrystallizations from tetrahydrofuran/chloroform gave the purified product as pale yellow crystals, mp 206.0-208.0.

EXAMPLE 5 O 2-Allylamino-3-chloro-5,6-dicyanopyrazine (3) was treated with liquid ammonia by condensing the am- N NC 01 [0 2CH2=CHCH2NH2 NC N 01 N NCIOINH-CH2CH=CH2 g 9 NC N Cl +CH2=CHCH2I 3C1 A solution of 5.00 g (25.1 mmoles) of 2,3-dichloro- 5,6-dicyanopyrazine in 50 ml of anhydrous tetrahydrofuran was cooled to in a Dry Ice/acetone bath and a solution of 3.00 g (52.6 mmoles) of allylamine in 20 ml of anhydrous tetrahydrofuran was added dropwise over a period of 30 minutes. After an additional 15 minutes the cold reaction mixture was poured into 700 ml of water giving an oil which crystallized to a yellow solid. The solid was filtered, washed with water and airdried to give 5.05 g of yellow solid 2-allylamino-3- chloro-5,6-dicyanopyrazine, mp 1 1 11l3. The product was purified by recrystallization twice from benzene/petroleum ether to give the purified product as pale yellow crystals, mp 1 13-l14.

IR (KBr): 2.98 y. (-NH); 3.23 p. (=CH); 3.42 t (saturated CH); 4.48 p. (-C I N); 6.09 t (terminal C=C); 6.31 p, 6.50 p., 6.62 p. (C=='C, C=N and/or --NH); 10.l2 ;1., 10.88 p. (CH=CH UV k f 347 mu (5 5000); 297 my, (6 22.800). NMR (CDCI multiplet, 4.23 6 (2H, allylic methylene);

multiplct 5.3 8 (2H, terminal olefinic); multiplet. 5.9 8 (1H. internal olefinic); broad singlet, 6.5 6(1H. N-H). Anal. Calcd for C H MCI:

C, 49.20; H. 2.73; N. 31.89; Cl, 16.17 Found: C. 48.96; H, 2.88; N 31.78; Cl, 15.92.

EXAMPLE A at once with stirring to 125 ml of hot (130F) water. A 5-g sample ofa multifabric swatch was immersed in the solution and it was heated at 100C for 1 hour with occasional swirling. The swatch was removed, rinsed well with distilled water and airdried. The dried swatch was examined under an ultraviolet light using an untreated swatch as a control.

2-Amino-3-chloro-5,o-dicyanopyrazine blue fluorescence was exhibited by the acetate, nylon, Arnel, and Verel T5 portions of the swatch, which showed incorporation of the compound.

2-Allylamino-3-chloro-5,o-dicyanopyrazine similar blue fluorescence was exhibited by the acetate, nylon, Arne], and Verel T5 portions of the swatch also showing incorporation of the compound.

When 2,3-dichloro-5,6-dicyanopyrazine is reacted as disclosed herein with the amines shown in Column A of Table l, the corresponding 2-substituted-amino-3- chloro-S,6-dicyanopyrazines shown in Column B of the 20 Table are obtained.

TABLE I N NC NHCQHS CgHsNHg Q NC \N/ (:1

N NC NHC4H9 c nnin 0 no c1 N NC/ \mtcmcng (CH3)2CHNH2 Q i NC c1 IN I NC --mic(cu (CH3)3CHH2 0 Cl NC\N/ N NCfO n(cna)cn(cn )z can-1c s)2 3 NC Cl n-c n mi N V ncf@ mzcsn -n no J01 TABLE I (continued) c NEiCeH -n n-C H ITH NC v 01 N no \N( c ns )c 4H9 C4H9NHC2H5 0 N (cbn mm O N NC I'l C3H7 C4H9 C4HQIIHCQH7 0 no 01 n c 1r CH2CII=CH2 2 (CH2=CHCZ-I2) 2m Q' NC 01 N N NC N(CI-I3)CH2CH=CHCH3 CH3CH=CHCEI2HHCH3 C) I claim:

wherein l. A compound of the formula ally are alkyl of 1-6 carbon atoms or alkenyl of 3 to 6 carbon atoms with the proviso that an unsaturated carbon of the alkenyl group is not directly attached to nitrogen.

2. A compound according to claim 1 where X NH,;

2-amino-3-chloro-5,-dicyanopyrazine. NC 11 X 3. A compound according to claim 1 where X IO NH-CH CH=CH 2-allylamino-3-chloro-5,6-

I dic ano razine. NC N Cl y py X is NH NHR or NRR' in which R and R individu- 

1. A compound of the formula
 1. A COMPOUND OF THE FORMULA
 2. A compound according to claim 1 where X NH2; 2-amino-3-chloro-5,6-dicyanopyrazine. 